Fix non-idempotent application sync for viewSorts (subFieldName undefined vs null) (#22505)

## Summary
Successive application syncs (`yarn twenty dev --once`) kept reporting
the same viewSorts as updated, even with no manifest changes. The
manifest converter never set `subFieldName`, so the manifest-derived
flat viewSort carried `undefined` where the flat viewSort computed from
the database carried `null`. The comparator (microdiff) treats `null` vs
`undefined` as a change, producing a phantom update action on every sync
that never converges — the resulting update is a no-op on the database.

Fixes twentyhq/core-team-issues#2629

## Changes
- **Converter**: `fromViewSortManifestToUniversalFlatViewSort` now sets
`subFieldName: viewSortManifest.subFieldName ?? null`, matching how the
sibling converters (e.g. view filters) handle optional compared
properties.
- **Type definition**: added optional `subFieldName?: string` to
`ViewSortManifest` in `twenty-shared`, mirroring `ViewFilterManifest` —
this also makes sorts on composite sub-fields (e.g. `amountMicros`)
expressible in app manifests, which the entity already supports.
- **Tests**:
- Asserts `subFieldName` is `null` (not `undefined`) when omitted — the
idempotency regression.
  - Asserts `subFieldName` is passed through when provided.

## Verification
- All 12 application-manifest converter suites pass (47 tests).
- Flat-entity comparison/constants suites pass (36 tests, 21 snapshots).
- `subFieldName` was already part of the viewSort compare properties, so
no comparator/constants changes needed.

https://claude.ai/code/session_018FrD42MMQtu1UvDyiEZbSq

<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/22505?utm_source=github"
rel="nofollow noreferrer noopener" target="_blank">``&lt;img alt="Review
in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"&gt;``</a>

packages/twenty-server/src/engine/core-modules/application/application-manifest/converters/__tests__/from-view-sort-manifest-to-universal-flat-view-sort.util.spec.ts

@@ -29,6 +29,23 @@ describe('fromViewSortManifestToUniversalFlatViewSort', () => {
     expect(result.createdAt).toBe(now);
     expect(result.updatedAt).toBe(now);
     expect(result.deletedAt).toBeNull();
+    expect(result.subFieldName).toBeNull();
+  });
+
+  it('should pass through subFieldName when provided', () => {
+    const result = fromViewSortManifestToUniversalFlatViewSort({
+      viewSortManifest: {
+        universalIdentifier: 'vsort-uuid-3',
+        fieldMetadataUniversalIdentifier: 'field-uuid-3',
+        direction: ViewSortDirection.ASC,
+        subFieldName: 'amountMicros',
+      },
+      viewUniversalIdentifier,
+      applicationUniversalIdentifier,
+      now,
+    });
+
+    expect(result.subFieldName).toBe('amountMicros');
   });
 
   it('should convert a view sort manifest with DESC direction', () => {

packages/twenty-server/src/engine/core-modules/application/application-manifest/converters/from-view-sort-manifest-to-universal-flat-view-sort.util.ts

@@ -20,6 +20,7 @@ export const fromViewSortManifestToUniversalFlatViewSort = ({
       viewSortManifest.fieldMetadataUniversalIdentifier,
     viewUniversalIdentifier,
     direction: viewSortManifest.direction,
+    subFieldName: viewSortManifest.subFieldName ?? null,
     createdAt: now,
     updatedAt: now,
     deletedAt: null,

packages/twenty-shared/src/application/viewManifestType.ts

@@ -61,6 +61,7 @@ export type ViewFieldGroupManifest = SyncableEntityOptions & {
 export type ViewSortManifest = SyncableEntityOptions & {
   fieldMetadataUniversalIdentifier: string;
   direction: ViewSortDirection;
+  subFieldName?: string;
 };
 
 export type ViewManifest = SyncableEntityOptions & {